用c语言建立一个链表，每个节点包括：学号、姓名、性别、年龄。

好的，下面是建立链表的代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// 定义链表节点结构体
typedef struct student {
    int number;
    char name[20];
    char sex;
    int age;
    struct student *next;
} Student;

// 初始化链表
Student *initList() {
    Student *head = (Student*)malloc(sizeof(Student));
    head->next = NULL;
    return head;
}

// 添加节点
void addNode(Student *head, int number, char name[], char sex, int age) {
    Student *p = (Student*)malloc(sizeof(Student));
    p->number = number;
    strcpy(p->name, name);
    p->sex = sex;
    p->age = age;
    p->next = NULL;
    
    Student *q = head;
    while (q->next != NULL) {
        q = q->next;
    }
    q->next = p;
}

// 删除节点
void deleteNode(Student *head, int number) {
    Student *p = head->next;
    Student *q = head;
    while (p != NULL) {
        if (p->number == number) {
            q->next = p->next;
            free(p);
            return;
        }
        q = p;
        p = p->next;
    }
}

// 修改节点
void modifyNode(Student *head, int number, char name[], char sex, int age) {
    Student *p = head->next;
    while (p != NULL) {
        if (p->number == number) {
            strcpy(p->name, name);
            p->sex = sex;
            p->age = age;
            return;
        }
        p = p->next;
    }
}

// 查询节点
void searchNode(Student *head, int number) {
    Student *p = head->next;
    while (p != NULL) {
        if (p->number == number) {
            printf("学号：%d\n", p->number);
            printf("姓名：%s\n", p->name);
            printf("性别：%c\n", p->sex);
            printf("年龄：%d\n", p->age);
            return;
        }
        p = p->next;
    }
    printf("查无此人！\n");
}

// 输出链表
void printList(Student *head) {
    Student *p = head->next;
    while (p != NULL) {
        printf("学号：%d\n", p->number);
        printf("姓名：%s\n", p->name);
        printf("性别：%c\n", p->sex);
        printf("年龄：%d\n", p->age);
        printf("\n");
        p = p->next;
    }
}

int main() {
    Student *head = initList();
    addNode(head, 1001, "小明", 'M', 18);
    addNode(head, 1002, "小红", 'F', 19);
    addNode(head, 1003, "小刚", 'M', 20);
    printList(head);
    deleteNode(head, 1002);
    printList(head);
    modifyNode(head, 1001, "小明明", 'M', 19);
    printList(head);
    searchNode(head, 1003);
    return 0;
}

这个程序实现了链表的基本操作，包括初始化链表、添加节点、删除节点、修改节点、查询节点和输出链表。你可以在此基础上进行修改，实现你所需的功能。